A vinyl chloride resin has the disadvantage that the workability during the molding process becomes insufficient due to a high melting viscosity, a low fluidity, and an easy thermal decomposition in some cases.
This was overcome by carrying a method for expanding a range of a temperature capable of molding the composition by compounding a plasticizer to a vinyl chloride resin. However, in this method, the plasticizer compounded during hot molding is volatilized, the complete achievement of the original target becomes difficult, and the mechanical property of the molded product decreases.
In order to address the above deficiencies, in a method for using a processing aid containing a copolymer of methyl methacrylate as a main component, the time to mold a sheet and a film by calender molding or extrusion molding is shorten. However, a melt (gelation) of a resin contained in the processing aid is reduced, and a molding at a broad processing range of from a lower temperature to a high temperature becomes difficult.
On the other hand, Patent Document 1 discloses a processing aid containing as a main component a known acrylonitrile-styrene copolymer. However, the vinyl chloride resin composition containing acrylonitrile-styrene copolymer disclosed in Patent document 1 does not meet a satisfactory workability during the molding process. In addition, in the resin composition, the surface property and gloss may be deteriorated due to the fish eye generated on the surface of the molded product. Further, a given acrylonitrile-styrene copolymer does not have sufficient transparency and yellow index in some cases.